A Pseudocolumn is like a table column, but it is not stored in the same table. We can select from a Pseudocolumn, but we can not insert, update or delete on a Pseudocolumn.
A Pseudocolumn is like a function with no arguments.
Two most popular Pseudocolumns in Oracle are ROWID and ROWNUM.
NEXTVAL and CURRVAL are also pseudo columns.Read the full book at www.amazon.com